This invention relates to aircraft environmental control systems and power systems, and more particularly to integrated environmental control, secondary power and emergency power systems.
Current integrated aircraft environmental control, secondary power and emergency power systems connect a compressor, power turbine and expansion turbine together using a single solid shaft. A single starter/generator is mounted on the same shaft. This arrangement forces all of the turbo-machine elements to rotate at the same speed. It is difficult to design all elements to operate at maximum efficiency at the same speed, since the power within the system must sum to zero and thus be balanced.
When applying thermal management considerations to the current system design, that design has limited operability due to surge margin and other inherent design limitations of the individual turbo-machine elements. The use of multiple elements on a single shaft results in a narrow operating window and margin. In addition, a long shaft is required to mount all of the turbo-machine elements. Furthermore, the use of a starter/generator requires a lower critical speed, and thus prevents operation at higher speeds. Current systems also use an air storage bottle to provide stored energy for high altitude emergency operation.
Ram air turbines and stored energy devices such as air bottles and hydrazine powered emergency power units (EPU) have been used as stand-alone emergency power devices. However, such systems are inoperative most of the time and contribute to increased aircraft weight and volume.
There is a need for an integrated apparatus that can provide environmental control, secondary power and emergency power.
This invention provides an apparatus for providing environmental control, secondary power and emergency power for an aircraft. The apparatus comprises a cooling turbine coupled to a first electromechanical machine rotor, and including an input for receiving compressed air or ram air, and an output for discharging cooled air or exhaust air; a compressor coupled to a second electromechanical machine rotor, and including an input for receiving engine bleed air or ambient air, and an output for discharging compressed air; means for magnetically coupling the first and second rotors; a power turbine coupled to the compressor; a heat exchanger connected between the compressor output and the cooling turbine input; and a control unit for controlling the magnetic coupling between the first and second rotors.
The means for magnetically coupling the first and second rotors can comprise a first stator winding magnetically coupled to the first rotor and a second stator winding magnetically coupled to the second rotor, and the control unit can comprise means for electrically connecting the first and second stator windings to each other. The control unit can connect voltage and/or current between the first and second stator windings using pulse code modulation.
The apparatus can further comprise a third stator winding and means for connecting the second stator winding and the third stator winding to a power source. A second control unit can be provided for driving the second rotor and the second stator as a motor. The first rotor, the second rotor, the first stator winding, the second stator winding and the third stator winding can be components of a switched reluctance machine.